Taking the following factors into account

such as the high penetration of distributed generation

the randomness of operation of DG

the active management scheme

the islanded operation mode

and multiple loads

as well as the influence of multivariate load on the safety protection for power distribution network

we proposed a divided-period adaptive overcurrent protection scheme based on time-varying characteristics of various influential factors. First

based on the fault output characteristic model of the grid connected DG

the characteristics of fault current in active distribution network were analyzed

and thus the effects of the above factors on the protection were qualitatively and quantitatively analyzed.Then

combined with distributed intelligence and centralized intelligence

a divided-period adaptive overcurrent protection system was built based on hybrid hierarchical management mode

and the hardware principle and software algorithm of each part of the system were introduced in detail. Finally

the protection scheme was simulated based on the MATLAB software to verify the effectiveness and rationality of the proposed scheme.